This invention relates generally to toilet tank fill valves.
The valve most commonly used in toilet tanks is a ballcock valve which is responsive to the level of water in the tank. When the toilet is flushed, the level of the water in the tank drops, causing a float to drop with the water level. As the float begins to drop, its weight causes the ballcock valve to open, allowing water to flow into the toilet tank from the main water supply. This type of system consequently allows water to flow into the toilet tank before the tank has been fully drained, thereby wasting a certain amount of water.
The conventional type of valve also has a number of parts which are prone to gradual deterioration, e.g. washers, O-rings, steel hinge pins, etc.. Such deterioration may cause water to leak from the main water supply into the tank from time to time. A further problem is that sand and dirt which are in the main water supply may become lodged in the valve seat, allowing water to escape from the main supply into the tank. This type of valve is also generally unable to prevent at least some backflow of tank water into the main water supply if the main supply is shut off.
Furthermore, many conventional valves generally do not readily allow for adjustment of the water level at which the inlet is closed, i.e. they do not readily allow for adjustment of the tank-full water level, and thus the volume of water to be used for the flush. In practice, when one wants to vary the water level in a tank using a conventional valve, one frequently just bends the lever arm which carries the float, to set the float to a different height for a given valve position, although in some cases the float arm may be threaded so that the float can be screwed up or down the arm.
One valve which does not allow for fairly simple adjustment of the tank-full water level is the valve described in U.S. Pat. Nos. 3,319,913, 3,429,333, and 3,495,803, in which the position of a float on a rod attached to the lever which actuates the ballcock valve can be changed. However, the valve described in these patents does not deal at all with the problem of the inlet valve opening before the tank is substantially emptied.